The lights start to dim, your Impala is running out of power, and then it stops running while you’re driving it — the alternator has gone bad. This part is likely to wear out at some point during vehicle ownership, so don’t be alarmed when it happens. Replacing an alternator isn’t a very difficult task, and doing it yourself will save you a lot of cash. Here’s how to change your Impala’s alternator at home with hand tools.
Step 1: Disconnect Your Battery
If you have a 2004 or newer Impala, keep in mind that disconnecting the battery can lead to system memory problems. Use a battery memory saver before you disconnect the battery.
You disconnect the battery to prevent any shorts that you may accidentally cause by touching a battery positive wire at the alternator. The surge in voltage could damage sensitive electronics in your Impala’s wiring.
Step 2: Remove the Alternator Drive Belt
On vehicles with a serpentine belt and tensioner, you’ll need to use a socket wrench with a long handle to pull the tensioner pulley out to give you enough slack to remove the belt. Take note of how it’s positioned because it can be confusing to put back on correctly, even though you have a diagram of the direction in the engine bay.
If you’re Impala has a belt for the alternator and no tensioner pulley, loosen the alternator pivot bolt and adjustment bolt to rotate the alternator out to remove the belt.
Step 3: Disconnect the Wiring from the Back of the Alternator
It’s usually easier to disconnect the wiring after removing the alternator bolts since you can rotate the alternator for easier access. However, you risk twisting the wires too much and damaging the connector or terminals — so it’s generally recommended that you remove the wiring before the alternator.
Know that some alternators have multiple wiring terminals on the back, so make sure you disconnect all wiring. Also, make a mental note of where it reconnects to prevent reinstalling the wiring in the incorrect positions.
Step 4: Unbolt and Remove the Alternator
Alternators usually have two or four mounting bolts. On alternators that can be adjusted, you’ll find two mounting bolts and a smaller bolt on the support bracket for adjustments. Alternators on Impalas with a tensioner pulley will have four mounting bolts to remove.
Step 5: Mount the New Alternator in Place
Install the mounting bolts and reconnect the wiring to the back of the alternator.
Step 6: Reinstall the Belt
Again, if your Impala has a tensioner pulley, you’ll need to pull that out to allow the serpentine belt to go back in place. Route it appropriately and make sure it’s in the correct position, this can be a little confusing so take your time.
If your Impala is older and doesn’t have the tensioner pulley, put the belt back on at the alternator as you took it off.
Additional Tips on Impala Alternator Replacement
- Do not disconnect the battery cable while the engine is running to test the health of your alternator. Doing this may cause voltage spikes that will damage the alternator.
- Test the battery to make sure it’s still good since a failed alternator can put a lot of strain on the battery. You’ll often find that battery failure shortly follows a dead alternator, and the same goes for a failing alternator after the battery dies.
- Use a battery charger to recharge the battery if it has run down before you start the vehicle — this will reduce load on your new alternator.
- If your belt has more than 60,000 miles on it, now is probably a good time to replace it to avoid risk of a slipping belt. Belts will less milage should still be inspected for damage and replaced if needed.
Only use a genuine GM alternator to ensure long lasting performance, and to avoid premature wear of the alternator or drain of the battery.